Technologies for modifying polymers are well known. Some polymer modification systems, for example, allow one to modify a polymer with ammonium salts, such that the ammonium salts will migrate to the surface. This has only been demonstrated with unbranched copolymer siloxane systems, which are different material than what is claimed in this invention. Prior art technologies generally rely upon standard linear polymers and copolymers.
For example, U.S. Pat. No. 5,567,372, “Method for Preparing a Nonwoven Web Containing Antimicrobial Siloxane Quaternary Ammonium Salts,” which issued to Nohr et al on Oct. 22, 1996, generally discloses a method for preparing a nonwoven web having antimicrobial properties which involves melting a melt-extrudable thermoplastic composition, extruding the molten composition through multiple orifices to form streams of molten composition, cooling the streams of molten composition to form fibers, and randomly depositing the fibers on a moving surface to form a web. The thermoplastic composition includes a thermoplastic material and an additive. The additive is an antimicrobial siloxane quaternary ammonium salt.
On the other hand, U.S. Pat. No. 5,620,788, “Wettable Polymeric Fabrics with Durable Surfactant Treatment”, which issued to Garavaglia et al on Apr. 15, 1997, discloses a polymeric fabric having enhanced wettability, a method for producing such wettable polymeric fabric, and a composition for use in the method. In one embodiment, the fabric includes a succinate surfactant substantially uniformly distributed on the surface of the fabric. The succinate surfactant is applied with a co-wetting aid, which reduces the surface tension of the surfactant composition. In another embodiment, the polymeric fabric comprises multiple surfactants on the surface of the polymeric fabric.
Additionally, U.S. Pat. No. 5,569,732, “Antimicrobial Siloxane Quaternary Ammonium Salts” which issued to Nohr et al describes a siloxane quaternary ammonium salt, which can be either of two general classes: (1) a trisiloxane having a pendent quaternary ammonium group and a molecular weight of from about 600 g/mol to about 1,700 g/mol; and (2) an ABA-type siloxane having a polydispersity of up to about 3.0 and a weight-average molecular weight of from about 800 g/mol to about 2,000 g/mol, in which a central siloxane moiety is terminated at each end by a quaternary ammonium salt group. The invention disclosed in U.S. Pat. No. 5,569,732 is generally directed toward the goal of providing a compound to be included as an additive in a thermoplastic composition for the preparation of antimicrobial nonwoven webs.
Other technologies exist whereby dendritic polymers have been used for coating applications. These materials are dendritic polymers with at least one anionic terminal group and a water-dispersible fluorine-containing component. Although a wide variety of polymer materials may be used, including polyester, polythioethers, and polyarylalkylenes, amine containing polymers are not acceptable materials for this application due to the fact that the high basicity interferes with the oxazoline polymer chemistry that forms the basis of their claims. A dendritic polymer coating, for example, is described in U.S. Pat. No. 5,731,095, “Dendritic Polymer Coatings,” which issued to Milco et al on Mar. 24, 1998. Milco et al discloses a water-soluble or water-dispersible fluorine-containing dendritic polymer surfactant having at least one terminal fluorocarbon moiety and at least one terminal anionic moiety. Such dendritic polymer coatings are apparently suitable for use in preparing protective coating compositions.
Currently, materials exist that can permit surface functional groups to be tailored by allowing equilibrium to drive the groups to the air interface. For example, it has been demonstrated that fluorinated groups can migrate to the surface and that under the same fluorine concentration, branching points in the polymer chain amplify the energetic interactions such that more fluorine is driven to the surface. To date, however, an extension to more highly branched systems has not been made or proposed.
Prior art technologies have been plagued with problems including high surfactant concentrations that can complicate processing and are inefficient, along with surface treatments that deposit functional groups of interest. Prior technologies do not provide a means of covalently linking the additive to the substrate. Furthermore, such prior art technologies also do not offer proper post-processing treatments.
Based on the foregoing, the present inventors have concluded that a need exists for a pre-organized chemical architecture that makes a greater and more efficient use of additives, thereby reducing the concentration required to observe migration to the surface during polymer surface modification procedures. The present inventors have also concluded that a need exists for polymer surfaces, which are stimuli-responsive to different environments, thereby causing different functional groups to migrate to the surface of such polymers.